Electrode development migration imaging method

ABSTRACT

A novel migration imaging system having a migration imaging member comrpising migration material in or on a softenable layer, also having a conductive receiving layer and a system for developing migration imaging members by applying a developing medium to an imaging member and having the imaging member adjacent a development electrode.

United States Patent 1191 Sankus, Jr. et al.

1451 Oct. 1, 1974 1 1 ELECTRODE DEVELOPMENT MIGRATION IMAGING METHOD[75] Inventors: Joseph G. Sankus, Jr., Fairport;

Alan B. Amidon, Penfield; William L. Goffe, Webster, all of NY.

[73] Assignee: Xerox Corporation, Rochester, NY.

[22] Filed: Sept. 2, 1969 [21] Appl. No.: 854,596

1521 Us. c1. 96/1 PS, 96/1.3 96/l.5

[51] Int. Cl 603g 13/00 [58] Field of Search 96/1.3, 1, 1.5, 1 PS [56] iReferences Cited UNITED STATES PATENTS 3,441,410 4/1969 Brynko 96/1 X3,510,419 5/1970 Carreira et a1 96/1.3 X 3,512,968 5/1970 Tulagin 96/1 X3,515,549 6/1970 Bixby 96/1 X 3,520,681 7/1970 Goffe 96/1.5 X 3,536,48310/1970 Watanabe et a1 96/1 3,556,781 1 1971 Levy et a1. 96/1 3,556,7831/1971 Kyriakakis 96/1 X 3,615,400 10/1971 Augostimi et 81.. 96/1 X3,653,064 3/1972 lnone et a1 96/1 Pc 3,653,885 4 1970 Levy et a1. 96/13,656,990 4/1972 Goffe 117/8 3,676,117 7 1972 Kimoshita 96/1 PrimaryExaminerRonald H. Smith Assistant Examiner-John R. Miller, Jr.

Attorney, Agent, or Firm-James J. Ralbate; David C. Petre; John B.Mitchell 5 7 ABSTRACT A novel migration imaging system having amigration imaging member comrpising migration material in or on asoftenable layer, also having a conductive receiving layer and a systemfor developing migration imaging members by applying a developing mediumto an imaging member and having the imaging member adjacent adevelopment electrode.

35 Claims, 18 Drawing Figures PAIENIEMBT 1 w 3.899.031 sum 1 u 4 FIG 2bPATENIEDUET H 3.839.031

summar ly FIG 5a F/G 5b ELECTRODE DEVELOPMENT MIGRATION IMAGING METHODBACKGROUND OF THE INVENTION This invention relates to a novel imagingsystem in which the recording material is selectively moved through andrepelled from a softenable medium under the influence of electricalforces.

Various methods of forming visible images in response to patterns oflights and shadows are well known. Recently, palpable, visible imageshave often been formed by means involving the electrical propertiesrather than the chemical properties of various photoconductivematerials. For example, a uniformly charged layer of photoconductivematerial is exposed to a pattern of light and shadows and the resultingelectrostatic latent image pattern is used to control the selectiveattraction or repulsion of a marking material onto the surface of thephoto-conductive layer thereby forming one type of electrostatographicimage.

More recently, however, a migration imaging system capable of producinghigh quality images of high density, continuous tone, and highresolution has been developed. Such a migration imaging system isdisclosed in copending application Ser. No. 460,377, filed June 1, 1965,now U.S. Pat. No. 3,520,681. In one embodiment of that system an imagingmember comprising a substrate layer with a layer of softenable materialoverlying the substrate and a third layer comprising photosensitiveparticles overlying the softenable layer, is imaged in the followingmanner: a latent image is formed on the member by suitable means, forexample, by uniformly electrostatically charging and exposing theuniformly charged member to a pattern of activating electromagneticradiation. The latently imaged member is then developed by exposing itto a solvent which dissolves only the softenable layer. Thephotosensitive particles of the third layer which have been exposed tothe radiation, migrate through the intermediate softenable layer as itis softened, depositing on the substrate an image of migratedphotosensitive particles corresponding to the radiation pattern to whichthe member was exposed. Where the softening step is performed by simplywashing the member in a suitable solvent, the material of the softenablelayer along with unmigrated residual portions of the upper layercomprising photosensitive particles, are substantially completely washedaway by the liquid solvent. The migrated particles imaged upon thesubstrate may then be fixed to the substrate. For many photosensitiveparticles which are preferred for use in such a migration imagingsystem, the image produced is a negative of a positive original.However, positive-to-positive imaging may be accomplished by varyingimaging parameters and materials.

The basic imaging member used in the new migration imaging system istypically in one of three configurations: (1) a layered configurationcomprising a substrate, coated with a layer of softenable material, anda fracturable and preferably particulate layer comprising photosensitivematerial on or embedded at the upper surface of the softenable layer;(2) a binder structure, in which the photosensitive particles aredispersed in the softenable layer overcoating the substrate; or, (3) anovercoated structure, in which a substrate is overcoated with a layer ofsoftenable material, followed by an overlayer comprising photosensitiveparticles, and a second overlayer of softenable material 2 sandwichingthe layer comprising photosensitive particles.

Softenableas used herein is intended to mean any material which can berendered more permeable thereby enabling particles to migrate throughits bulk. Conventionally, changing permeability is accomplished by heator solvent softening. Fracturable" layer or material as used herein,means any particulate, continuous, or semi-continuous layer or materialwhich is capable of breaking up during development, thereby permittingportions of said layer to migrate towards the substrate or to beotherwise removed.

There are other systems for forming the latent image, whereinnon-photosensitive or inert, fracturable layers or particulate materialmay be used to form said images, as described in copending applicationSer. No. 483,675, tiled Aug. 30, 1965, now U.S. Pat. No. 3,656,990. Inthat application and copending application Ser. No. 725,676, filed MayI, 1968, now abandoned, as well as the present application, a variety ofmethods which may be used to form the latent image upon the migrationimaging member are disclosed.

Likewise, various means for developing latent images in the novelmigration imaging system are known. Typi cal developing means includesolvent washaway, as described above, solvent vapor softening, heatsoftening and combinations of these methods. In another mode ofdevelopment, if the softenable layer is at least partially left behindon the substrate, it has been found that the unmigrated fracturablematerial remaining on the imaging member after development may beadhesively stripped off to yield complementary positive and negativeimages, as disclosed for example, in copending application Ser. No.642.8 30, filed June 1 1967 now U.S. Pat. No. 3,740,216.

In new and growing areas of technology such as migration imaging systemssuitable for use in the present invention, new methods, apparatus,compositions of matter, and articles'of manufacture continue to bediscovered for the application of the new technology in a new mode. Thepresent invention relates to a new and advantageous system for thedevelopment of latent images in such migration imaging systems. I

SUMMARY OF THE INVENTION It is, therefore, an object of this inventionto provide a novel imaging system.

It is another object of this invention to provide a novel imaging systemwherein marking material is selectively displaced in imageconfiguration.

It is another object of this invention to provide a novel imaging systemwherein photosensitive material is selectively displaced in imageconfiguration.

It is another object of the invention to provide a novel imaging member.

It is another object of this invention to provide a development systemfor migration imaging members, which system produces high quality imagesof high resolution, low background, and excellent solid area coverage.

It is another object of this invention to provide images having lesseramounts of extraneous marking materials in background (non-image) areas.

It is another object of this invention to provide an imaging systemcapable of positive-to-positive, or positive-to-negative imaging.

It is 'yet another object of this invention to provide an imaging systemcapable of producing complementary negative and positive images from thesame imaging member.

It is still another object of this invention to provide a migrationimaging system which is more suitable for automatic imaging apparatus.

The foregoing objects and others are accomplished in accordance withthis invention by the novel migration imaging system, comprising amigration imaging member comprising migration material in or on asoftenable layer said member having a conductive receiving layer, and asystem for developing migration imaging members comprising applying adeveloping medium to an imaging member and having said member adjacent adevelopment electrode.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of theinvention as well as other objects and further features thereofreference is made to the following detailed disclosure of the preferredembodiments of the invention taken in conjunction with the accompanyingdrawings thereof, wherein:

FIGS. 1(a) and 1(1)) show partially schematic crosssectional views (a)and (b) of typical migration imaging members suitable for use inpreferred embodiments of the inventive system.

FIGS. 2(a) to 2(d) illustrate process steps suitable for usein apreferred embodiment of the inventive system.

FIGS. 3(a) to 3(e) illustrate the process steps in another preferredembodiment of the present inventive system.

FIGS. 4(a) and 4(b) show cross-sectional views of preferred embodimentsof the novel migration imaging member of the present invention.

FIGS. 5(a) to 5(e) illustrate the process steps in another preferredembodiment of the present inventive system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, oneembodiment of an imaging member suitable for use in a migration imag ingsystem is shown in a partially schematic view in FIG. 1(a). Thistypically comprises a substrate 11 coated with a layer of softenablematerial 12 in which particles 13 of a suitable marking material aredispersed. Another embodiment of a migration imaging member is shown inFIG. 1(b) wherein the member 10 typically comprises substrate 11 coatedwith layer of softenable material 12, and fracturable or particulatelayer 13 comprising migration marking material is contiguous the uppersurface of the softenable layer. In various embodiments, the markingmaterial may be coated onto, slightly embedded in, or substantiallyembedded in the softenable material of layer 12 at the upper surface ofthat layer.

The substrate and other layers of the migration imag ing member maygenerally be in any suitable form such as a strip, sheet, plate, coil,cylinder, drum, endless belt, circular disk or the like, depending uponthe specific embodiment of the novel migration imaging system.

In various embodiments of the inventive imaging system, the preferredsubstrate may be electrically conductive or insulating. However, incertain embodiments the substantially electrically insulating substrateis the more preferable substrate. In addition. the substrate should besubstantially insoluble in any solvent which may be used for developingsuch migration imaging members.

The softenable layer may be coated directly onto the insulatingsubstrate, or alternatively, the softenable layer may be formedseparately from the desired substrate and may be brought into contactwith a suitable substrate during imaging. The softenable layer maycomprise one or more layers of softenable material. The softenable layershould preferably be substantially electrically insulating for use inpreferred modes of migration imaging by applying electrical migrationforces to the migration layers; but, more conductive materials may beused in other electrical modes of the imaging system wherein a constantand replenishing supply of charges in image configuration is applied tothe imaged member. The softenable layer may be of any suitablethickness. However, imaging thicker layers generally requires a greaterelectrostatic potential in a given mode of the migration imaging system.Thicknesses in the range of about /2 to about 16 microns have been foundpreferable for use in such imaging systems.

Materials suitable for use as softenable layers and marking materials insuch migration imaging systems, are more fully discussed in copendingapplications Ser. No. 725,676, filed May I, 1968, now abandoned, andSer. No. 634,757, filed Apr. 28, 1967, now abandoned. Marking materialssuitable for use in migration imaging members may be insulating,conductive, magnetic, or photosensitive in various embodiments of theimaging member. In the preferred electro-optical mode of migrationimaging, the migration marking material is typically electricallyphotosensitive.

The electrically photosensitive material or particles, portions of whichmigrate during image formation, may comprise any suitable electricallyphotosensitive material which is not readily soluble in any of the mediaused to soften the softenable layer during development of the migrationimaging member. Preferably, photosensitive materials in particle formshould be about 0.01 to about 3 microns in size and optimally about 0.5to about 1 microns in size for optimum resolution and otherwise highquality images according to this invent1on.

Electrically photosensitive particles as used herein refers to anyparticles which when dispersed in a softenable, electrically insulatingbinder or matrix layer as described herein, in response to electricalcharging, imagewise exposure to activating radiation, and contact withsuitable softening media, are caused to selectively deposit in positiveor negative image configuration on a substrate or on an appropriatereceiving layer.

While photoconductive particles, (and photoconductive" is used in itsbroadest sense to mean particles which show increased electricalconductivity when illuminated with electromagnetic radiation and notnecessarily those which have been found to be useful in xerography inxerographic pigment-binder plate configurations) have been found to be aclass of particles useful as electrically photosensitive particles inthis invention and while the photoconductive effect is often sufficientin the present invention to provide an electrically photosensitive"material, it does not appear to be a necessary effect. Apparently thenecessary effect according to the invention is the selective relocationof charge into, within or out of the material or particles, saidrelocation being effected by light acting on the bulk or surface of theelectrically photosensitive material, by exposing said material orparticle to activating radiation which may specifically includephotoconductive effects, photoinjection, photoemission, photochemicaleffects and others which cause said selective relocation of charge.

Materials typically suitable for use as insulating substrates includefilms of polystyrene; cellulose acetate; polyester films such aspolyethylene terephthalate film (e.g., Mylar available from Dupont);polyamide films such as those prepared from caprolactam Nylon 66;polyolefin films such as extruded polyethylene or biaxially orientedpolypropylene; films prepared from polyacrylonitrile and copolymersthereof; plastic coated papers; acrylic sheets such as Lucite; glass;films of polytetrafluoroethylene and poly chloro-fluoro ethylene resinssuch as Duponts Teflon and 3Ms Kel-F; mixtures and combinations of theabove, and other insulating materials generally known in the art.

Particularly satisfactory insulators include Mylar polyester filmavailable from the E. I. duPont deNemours Co., Inc., usually used in athickness from about 2 to 5 mils; and polyethylene coated paperavailable under the tradename Polygleam available from Crocker-HamiltonDivision of Weyerhaeuser Corporation.

Materials typically suitable for use as electrically conductivesubstrates include: copper, brass, nickel, zinc, chromium, stainlesssteel, conductive plastics and rubbers, aluminum, steel, cadmium,silver, gold or paper rendered conductive by the inclusion of a suitablechemical therein or through conditioning in a humid atmosphere to ensurethe presence therein of sufficient water content to render the materialconductive. If desired, the conductive substrate may be coated on aninsulator such as paper, glass, or plastic. One example of this type ofsubstrate comprises NESA glass, which is substantially transparent tinoxide coated glass available from Pittsburgh Plate Glass Co. Anothertypical substrate comprises aluminized Mylar which is made up of a Mylarpolyester film available from the E. I. duPont deNemours Co., Inc.,having a thin, substantially transparent aluminum coating. Anothertypical substrate comprises Mylar coated with copper iodide. Othersinclude conductive resin coated films such as Dow Resin 2611-7 (DowChemical Company) or Conductive Polymer 261 (Calgon Corporation).

The imaging method illustrated in FIG. 2 includes an optionalprecharging step as first disclosed in copending application Ser. No.645,192, filed June 12, 1967, now abandoned. It is seen in FIG. 2(a),that the imaging member 10 comprising marking particles 13, which arehere electrically photosensitive particles, dispersed in softenablelayer 12 coated on a substantially electrically insulating substrate 11,is placed upon a grounded conductive member 14 and the imaging member ischarged with a negative polarity at 15 while being uniformly floodedwith activating electromagnetic radiation, light for example, fromsource 16. In FIG. 2(b), the source of activating radiation,.here light,has been removed, and a positive electrostatic charge is then applied tosurface 17 of the imaging member by a corona charging device 18 or otherequivalent means while maintaining the imaging member in darkroomconditions as disclosed in Steinhilper US. Pat. No.

2,955,938. In FIG. 2(0), the charged imaging member is exposed to apattern of activating electromagnetic radiation, such as light, exposingthe charged imaging member in areas 20 and leaving it unexposed in areas21, thereby forming an electrostatic latent image or other electricallatent image which may be developed by any suitable developmenttechnique.

An electrical latent image is intended to mean any electrical imagewisemigration force acting on the charged marking materials in the presentsystem. This includes electrostatic latent images" which are well knownin the xerographic arts and are detectable with equipment such as aMonroe Electrometer, available from Monroe Electronics, Webster, N.Y.,which measures surface potentials and differences in surface potentialto a sensitivity of about -5 volts. The latent images formed in theelectrical-optical mode of the present invention are typically notreadily detectable by such electrometric techniques. In contrast to anelectrostatic latent image, for example as found in commercialxerographic processes using an amorphous selenium photoconductor wheresurface potentials in image areas typically differ by at least about 600volts,

the latent images formed in the preferred chargeexpose mode of thepresent system typically show no readily detectable change in theelectrostatic or cou lombic force after exposure, although migration inimage configuration still occurs when the softenable material issoftened.

FIG. 2(d) illustrates the imaged migration imaging member beingdeveloped by exposure to liquid solvent 22 in a system including noveldevelopment electrode 23 of the present inventive system. Thedevelopment electrode may be grounded, or electrically biased.Development electrode 23 enhances the removal of unmigrated markingparticles from background areas 24 of an imaged migration imagingmember, thereby facilitating production of sharp, positive images 25 ofexcellent resolution, low background, and excellent solid area coverageupon the substrate ofthe imaging memher.

It will be appreciated that through the use of selected materials, thesequence of the charging polarities may be reversed thereby utilizing apositive charge first and a negative charge second. In addition, thesurface of the imaging member may optionally be flooded with lightfollowing the optional initial charging step rather than simultaneouslywith it, while still achieving the desired result of uniform charging.

The novel imaging system of the present invention differs from formermigration imaging systems and particularly from former migration imagingdevelopment systems in that in the advantageous system of the presentinvention unmigrated marking par'ticlesare repelled from the imagingmember and attracted to the development electrode, whereas in formersystems, the primarymovement of marking particles was the movement ofparticles in unexposed imaged areas'of the migration imaging membertoward the substrate of said member. In the inventive system as shownand described in FIG. 2, during the optional charging step with ambientlight as illustrated in FIG.2(a) it is believed that negative chargecarriers are forced to interface 19 between the softenable layer and thesubstantially insulating substrate, and that such charges are trappedthere by the attraction of the opposite charge in the conductive,grounded member '14. When the source of activating radiation, herelight, is removed, it is believed that negative carriers are trapped atinterface 19. Then, during the positive charging step illustrated inFIG. 2(b) it is believed that corresponding negative charge from theconductive ground allows the imaging member to be positively charged atthe surface, and negatively charged at interface 19. During the exposurestep illustrated in FIG. 2(c), the charges trapped on the imaging memberduring the charging steps are dissipated in the background areas as theimaging member is affected by the activating radiation, here light.

Migration imaging members have typically been developed by exposure toliquid solvents, vaporous solvents, or exposure to heat, sufficient tosoften the softenable layer of the imaging member. In former developmentsystems, the primary movement of marking particles was, typically, themovement of particles in the unexposed imaged areas toward the substrateof the migration imaging member. However, suprisingly, the

advantageous system of the present invention by its imagewise repulsionprocess gives rise to positive images upon the substrate of the imagingmember. Quite unexpectedly it is found that there is an imagewiserepulsion of charged particles from the illuminated background areas ofthe imaged member to the grounded development electrode. In this processthe marking particles which are freed from the matrix of the softenablelayer by the action of the solvent upon said softenable layer, areobserved to quickly migrate away from the migration imaging member andadhere to the grounded development electrode. In this way substantiallyall of the marking particles in the illuminated background areas of theimaged member are removed from the member itself, leaving a positiveimage of excellent quality upon the substrate of the imaging member. Thepresent system is most advantageous in that there is an even lessertendency than in earlier systems for unmigrated marking particles toremain in background areas of the imaged member.

The development electrode 23 illustrated in FIG. 2(d) may be made of anysuitable conductive material. The obvious limitation is that theelectrode be substantially unaffected by the solvent being used for thedevelopment of the imaging member. Aluminum, copper, stainless steel,and other metallic conductors, tin oxide coated NESA glass availablefrom Pittsburg Plate Glass Co., metallized Mylar film available fromDupont, paper coated with evaporated aluminum or conductive resincompositions, and even highly humidified papers and cellophane films aresuitable for use as electrode materials in the present invention. Thedevelopment electrode is typically electrically grounded or electricallybiased in order to promote the development process. Electrical biases inthe range of about -200 volts are suitable for use in the inventivesystem. Depending upon the specific materials used, either positive ornegative polarity may be applied to the development electrode.

FIG. 3 illustrates the process steps in another preferred embodiment ofthe advantageous imaging system of the present invention. In FIG. 3(a),a migration imaging member such as that illustrated in FIG. 1, isnegatively charged by corona charging device 26 in the presence of light27. The light is then removed, and as shown in FIG. 3( b), the imagingmember is positively charged by corona device 28. The charged imagingmember then remains positively charged at its upper surface 29, andnegatively charged at the interface 30 between the'softenable material12 and the substrate 11. In FIG. 3(a), the positively charged imagingmember is shown being exposed to a Iight-and-shadow image with lightimpinging upon the member at 31, and the unexposed imaged areasremaining charged at 32. FIG. 3(d) shows an imaged member to whichconductive receiving layer 33 has been applied, and to which adeveloping medium is being applied through said conductive receivinglayer by means of roller 34. It will be understood that the developingmedium may be ap- I plied by any one of a variety of means including theillustrated solvent roller, a solvent spray system, a solvent bath,various means for applying vaporous solvents, or various means forapplying heat. It will 'be appreciated that the developing medium willtypically be sufficiently electrically resistant to permit migration ofthe marking material before the imaging member is discharged.

In the development step illustrated in FIG. 3(d), the conductivereceiving sheet is electrically grounded or electrically biased andperforms the function of the development electrode illustrated in FIG.2(d).

After the application of the development medium which softens thesoftenable layer of the imaging member, in the presence of thedevelopment electrode which is here in the form of the conductivereceiving sheet, said receiving sheet is removed from the migrationimaging member as shown in FIG. 3(e), andin this mode of theadvantageous migration imaging system, the positive image 35 is adheredto the conductive receiving layer 33. The substrate 11, which in theembodiment illustrated in FIG. 2, supported the positive image, heresupports the negative image 36 corresponding to the positive image 35which has been transferred to the conductive receiving layer 33.Surprisingly, when the development electrode, here the conductivereceiving layer, is itself in contact with the imaging member, the imageproduced on the substrate of the member is a negative of the original,and the image on the receiving layer is the positive image.

Where the conductive receiving sheet is in contact with the exposedimaging member, the spacing between the charged migration markingparticles and the receiving sheet becomes small compared to the spacingbetween the charged particles and the induced counter-charge at thesubstrate interface with the softenable material. Therefore it isbelieved that the capacitance between the particles and the conductivereceiving sheet becomes larger than the capacitance between the chargedparticle and its corresponding induced counter-charge. Hence, theelectric field lines of force are re-directed from particle to receivingsheet in proportion to this capacitance ratio, and the particle is thenattracted to the receiving sheet, thereby producing a positive image ofa positive original on the receiving sheet. This theory is believed toexplain the image reversal in the process illustrated in FIG. 2 ascompared with the process illustrated in FIG. 3.

It is therefore seen that in the preferred embodiment of the presentmigration imaging system illustrated in FIG. 3, the conductive receivinglayer 33 is itself typically not substantially soluble in thedevelopment medium used, and it is also sufficiently conductive toperform the function of the development electrode in the developmentsystem. It is also most advantageous for ample fixing methods andmaterials are disclosed in copending applications Ser. No. 590,959,filed Oct. 31, 1966, now abandoned, and Ser. No. 695,214, filed Jan. 2,1968, now abandoned.

FIG. 4 illustrates novel imaging members for use in another preferredembodiment of the present inventive system. The novel migration imagingmember in FIG.

4(a) comprises substrate 11 supporting softenable layer l2 whereinmarking particles 13 are dispersed. and conductive receiving layer 33overlying the matrix of softenable layer and marking particles. In Fig.4(b) the novel migration imaging member comprises substrate 11supporting softenable layer 12(i) over which fracturable layer 13 ofmarking material is coated or embedded. This embodiment further includesa second softenable layer 12 (ii) coated over marking material 13.Conductive receiving layer 33 overlies the softenable layers 12(ii).

Materials suitable for use in the substrate, softenable layer, andmarking material portions of the novel migration imaging member are thesame as those described as suitable for use in the migration imagingmember illustrated in FIG. 1 above.

Materials which have been found suitable for use as conductive receivinglayer 33 in the novel imaging member in the advantageous system of thepresent invention include conductive papers such as 48 l electrostaticbase stock, 60 No., West Virginia Pulp and Paper Company; ConductiveCopy Base A No. 7850-8, from Crocker Hamilton Papers, a division ofWeyerhauser Corporation; moistened 914 Bond, Xerox Corporation; ZincOxide Paper, Bruning Pre- 1 mium, Charles Bruning Company; PolyvinylAlcohol OS Base, type P-1096, 1997-0, 45No., Standard color, Lot No.18949, Crocker Hamilton; Conductive Base Copy C, No. 168118, L-01-41-2,45 No., Crocker Hamilton; Conductive Copy Base, D-ll9- 13-2, 39 No.,69330, Crocker Hamilton; Conductive Copy Base A, No. 63678, K-0l-40-2,45 No., Crocker Hamilton; and electroconductive papers (containingsilver treated glass fiber) from P. J. Schweitzer Division of KimberlyClark Company having surface resistivities in the range of about 2 toabout 500 megaohms per square; and any other suitable conductive,preferably porous material. Conductive receiving layers havingresistances of less than about 10 ohm-cm, and thicknesses less thanabout 200 microns are preferred for use in the present system.

In FIG. 5 yet another preferred embodiment of the advantageous inventionof the present system is illustrated using the novel migration imagingmember illustrated in FIG. 4. FIGS. 5(a) and (b) illustrate the doublecharging procedure already described in conjunction with FIGS. 2(a) and(b), and 3(a) and (b). In FIG. 5(0), the novel migration imaging memberalready charged as illustrated in FIGS. 5(a) and (b), is shown beingimaged by exposure through the substantially transparent base material38. In FIG. 5(d), the developing medium is being applied as discussed inconjunction with FIG. 3(d), and in FIG. 5(e), the complementary negativeand positive images are shown being separated, with the positive imageadhering to the conductive receiving layer. and the correspondingnegative image remaining on the substantially insulating substrate, asdiscussed with respect to FIG. 3(e).

Yet another preferred embodiment of the advantageous system of thepresent invention uses the process steps essentially the same as thoseshown in FIG. 5, except that the novel migration imaging member isexposed through a conductive receiving layer which is substantiallytransparent. It will be appreciated that a receiving layer for use inthis process must necessarily be transparent to allow sufficient lightor other electromagnetic radiation to pass therethrough so that a sharpimage is formed by the unexposed areas on the imaging member. As inother embodiments of the advantageous system of the present invention,the softening step and the separation step may be performed by anysuitable means.

The following examples further specifically define the advantageousmigration imaging system of the present invention. The parts andpercentages are by weight unless otherwise indicated. The examples beloware intended to illustrate various preferred embodiments of the imagingsystem of the present invention.

EXAMPLE I A migration imaging member suitable for use in the presentinventive system is constructed using a matrix of photosensitiveparticles in a softenable material, said matrix consisting of an about1:3 ratio of x-form metalfree phthalocyanine to Piccopale -SF, apetroleum hydrocarbon resin with a color of G-lO on the Gardner scale,which is available from Pennsylvania Industrial Chemical Co., and saidmatrix is ground in a long-chain saturated aliphatic hydrocarbon liquid,boiling point 3 l5350F., lsopar G solvent, available from Humble OilCo., thoroughly mixed on a paint shaker, and coated onto an insulatingMylar polyester film, available from E. l. duPont deNemours and Co.,Inc., of about 3 mils in thickness. The imaging member is then dried for10 minutes at about 50C.

The above imaging member is then laid on an electrically groundedconductive base plate, with the exposed side of the Mylar film incontact'with the conductive base plate. In ambient illumination, theimaging member on the conductive base plate is negatively charged.

Then in darkness, the imaging member still on the conductive base plateis recharged positively. The charged imaging member is then exposed to apattern of lightand-shadow images illuminated to about 0.8 fcs(footcandle-seconds) of tungsten illumination. The imaging member thensupporting an electrostatic latent image is developed by immersion inxylene solvent while the side of the imaging member supporting themigration material is closely spaced adjacent to a grounded metalelectrode within the solvent bath.

This imaging member and process gives sharp, clean positive images withvery low background, on the original Mylar substrate, and correspondingnegative images on the development electrode.

EXAMPLE II A migration imaging member suitable for use in a preferredembodiment of the present inventive system is produced using a sheet ofPolygleam polyethylene coated paper from Crocker Hamilton PapersDivision, Weyerhauser Paper Company, Fitchburg, Mass, as the insulatingsubstrate. The Polygleam substrate is coated with a layer of amicro-imaging matrix comprising about a 1:3 ratio of x-form metal-freephthalocyanine to Piccopale 70-SF (thermoplastic hydrocarbon resin)which is ground in lsopar G solvent, and thoroughly mixed on a paintshaker. The matrix coating is applied using an 0.0005 inch Birdapplicator bar and a mechanical drive unit from Gardner Laboratories,lnc. The migration imaging member is then air dried for half an hour.

The imaging member is then charged negatively in the presence of ambientillumination. Then in darkness, the imaging member is chargedpositively. Next the charged imaging member is exposed to alight-andshadow image of about 20 fcs (foot-candle-seconds) of lightproduced from a tungsten filament at about 2,800K projected through apositive transparency. A sheet of water vapor pre-moistened 914 Xeroxbond paper (Xerox Corp., Rochester, N.Y.) is placed in contact with theside of the migration imaging member containing the migration material,and the developing solvent, Freon 1 l3, trifluoro trichloroethane,manufactured by E. l. duPont deNemours and Co., Wilmington, Delaware, isapplied through the conductive receiving sheet. A type 72Q inchdiameter, 4 inch wide, gravure roller, available from Parmarco lnc.,Roselle, N. J is passed over the receiving sheet once with moderatemanual pressure. The receiving sheet is then separated from the imagingmember.

A positive image is obtained on the conductive receiving sheet, and acorresponding negative pattern remains on the Polygleam substrate of theimaging member. Upon drying, the sharp, positive image on the conductivereceiving sheet becomes fixed within and to the receiving sheet. Thenegative image on the Polygleam substrate of the imaging member remainsunfixed due to the nearly complete removal of the matrix binder in thedevelopment step.

EXAMPLE III A migration imaging member is prepared and processed as inExample 1, except the exposure step is performed through the transparentMylar substrate which is in contact with the electricallygrounded'conductive base plate which is a sheet of substantiallytransparent tin oxide coated NESA glass available from the PittsburghPlate Glass Co.

EXAMPLE IV A migration imaging member suitable for use in a preferredembodiment of the inventive system is produced using a matrix ofphotosensitive particles in a softenable material, said matrixcomprising about 10 grams of elemental selenium alloyed with arsenic(two percent by weight of arsenic), about 5 grams of a copolymer ofhexylmethylacrylate and styrene and about 13 grams of toluene, which ismilled in a ball mill jar with flint balls of size 000 for about 96hours. The milling balls arethen removed from the solution, and thematrix solution is coated onto a Mylar polyester substrate,,availablefrom duPont, with a Gardner Draw This imaging member is then imaged bythe process of Example 1, and is developed by immersing it for a fewseconds adjacent a grounded metal electrode in a trichloroethylene bath.This imaging member and process gives sharp, clean images with very lowbackground.

EXAMPLE V A migration imaging member is prepared using the binder matrixdescribed in Example ll coated onto an electrically conductivealuminized Mylar film, an aluminum coated polyester film available fromduPont, as the substrate. This imaging member is charged. exposed anddeveloped as in Example ll, using a sheet of pre-moistened 914 Xeroxbond paper as the conductive receiving sheet and Freon l 13, trifluorotrichloroethane solvent as the developing medium. Images similar tothose produced in Example [I are produced by this system.

Although specific components, proportions and procedures have beenstated in the above description of the preferred embodiments of thenovel migration imaging system, other suitable materials, as listedabove, may be used with similar results. In addition, it may be thatother substances exist or may be discovered, that have some or enough ofthe properties of the particular substances described herein to be usedas substitutes, or that other materials and procedures may be employedto synergize, enhance or otherwise modify the novel migration imagingsystem.

Such other modifications and ramifications of the present invention willoccur to those skilled in the art upon a reading of this disclosure.These are intended to be included within the scope of this invention.

What is claimed is: a

1. An imaging method comprising:

providing an imaging member comprising a substrate supporting a layer ofsubstantially electrically insulating softenable material containingmigration marking material, said softenable material capable of havingits resistance to migration of migration marking material decreasedsufficiently to allow migration of migration marking material in depthin said softenable layer,

forming an electrical latent image on said member,

and thereafter placing an electrically conductive receiving layer incontact with the softenable layer of the imaging member, saidelectrically conductive receiving layer being electrically biased orelectrically grounded, and

developing said member by decreasing the resistance of the softenablematerial to migration of migration marking material in depth in thesoftenable material at least sufficient to allow migration of migrationmarking material at least in depth in said softenable material wherebythe migration marking material selectively migrates in a first imageconfiguration toward said conductive receiving sheet and in a secondimage configuration complementary to said first image configurationtoward said substrate.

2. The method of claim 1 wherein the conductive receiving layer ispermeable to a fluid solvent.

3. An imaging method comprising:

providing an imaging member comprising a substrate supporting a layer ofsolvent soluble electrically insulating material containing migrationmarking material,

forming an electrical latent image on said imaging member,

providing an electrode closely spaced adjacent the free surface of saidlayer of solvent soluble electrically insulating material, saidelectrode being electrically grounded or electrically biased without aninsulating blocking layer between said imaging member and saidelectrode, and

providing a liquid solvent for said solvent soluble material betweensaid layer of said solvent soluble material and said electrode wherebymigration marking material selectively migrates in a first imagewiseconfiguration toward said substrate and in a second imagewiseconfiguration complementary to said first imagewise configuration towardsaid electrode.

4. The method of claim 3 wherein said substrate is substantiallyelectrically insulating.

5. The method of claim 4 wherein the migration marking material isparticulate material and said particulate migration marking material isdispersed throughout the layer of solvent soluble material.

6. The method of claim '4 wherein the migration marking material is inthe form of a fracturable layer of migration marking material contiguousthe surface of the layer of the solvent soluble material spaced apartfrom the substrate.

7. The method of claim 6 wherein the imaging member additionallycomprises a second layer of solvent soluble electrically insulatingmaterial overlying the fracturable layer of migration marking material.

8. The method of claim 3 wherein the solvent is provided between thelayer of solvent soluble material and the electrode by placing saidimaging member and said electrode in a volume of said solvent.

9. The method of claim 4 wherein the migration marking materialcomprises electrically photosensitive material.

10. The method of claim wherein the migration marking material compriseselectrically photosensitive material.

11. The method of claim 9 wherein the electrical latent image isprovided by steps comprising substantially uniformly electrostaticallycharging the surface of the imaging member, and imagewise exposing saidmember with an image pattern of activating electromagnetic radiation.

12. The method of claim 10 wherein the electrical latent image isprovided by steps comprising substantially uniformly electrostatically'charging the surface of the imaging member with a charge of a firstpolarity, and imagewise exposing said member with an image pattern ofactivating electromagnetic radiation.

13. The method of claim 12 wherein before performing the charge andexpose steps of claim 12the imaging member is pre-charged by stepscomprising:

contacting the electrically insulating substrate to an electricallygrounded electrically conductive member, and

substantially uniformly electrostatically charging said member with acharge of opposite polarity from said first polarity, whilesimultaneously substantially uniformly flooding said member withactivating electromagnetic radiation.

14. The method of claim 12 wherein the migration marking material in theimagewise unexposed areas of the imaging member migrate in said firstimagewise configuration toward the electrically insulating sub: strate,and the migration marking material in the imagewise exposed areas of theimaging member migrate in said second imagewise configurationcomplementary to said first imagewise configuration toward saidelectrode.

15. The method of claim 3 wherein said layer of solvent soluble materialis of a thickness in the range between about /z'and about 16 microns.

16. The method of claim 3 wherein said migration marking material isparticulate material of average particle size in the range between about0.01 and about 3 microns.

17. The method of claim 16 wherein said particulate migration markingmaterial is of average particle size in the range between about 0.5 andabout 1 micron.

18. The method of claim 1 wherein said substrate is substantiallyelectrically insulating.

19. The method of claim 1 wherein said substrate is substantiallyelectrically conductive.

20. The method of claim 1 wherein said substrate is substantiallytransparent.

21. The method of claim 1 wherein the migration marking material isparticulate material and said particulate migration marking material isdispersed throughout the layer of softenable material.

22. The method of claim 1 wherein the migration marking material is inthe form of a fracturable layer of migration marking material contiguousthe surface of the layer of softenable material spaced apart from thesubstrate.

23. The method of claim 22 wherein the imaging member additionallycomprises a second layer of substantially electrically insulatingsoftenable material overlying the fracturable layer of migration markingmaterial.

24. The method of claim 1 wherein the migration marking materialcomprises electrically photosensitive material. v

25. The method of claim 24 wherein the electrical latent image isprovided by steps comprising substantially uniformly electrostaticallycharging the surface of the imaging member with a charge of one polarityand imagewise exposing said member with an image pattern of activatingelectromagnetic radiation.

26. The method of claim 24 wherein said layer of substantiallyelectrically insulating softenable material is of a thickness in therange between about /2 and about 16 microns.

27. The method of claim 1 wherein said migration marking material isparticulate material of average particle size in the range between about0.01 and about 3 microns.

28. The method of claim 27 wherein said particulate material is ofaveage particle size in the range between about 0.05 and about 1 micron.

29. The method of claim 1 wherein said member is developed by applying aliquid solvent for said softenable material to the imaging memberwhereby portions of said electrically insulating layer and selectiveportions of said migration marking material are removed and selectiveother portions of said migration marking material migrate at least indepth toward said substrate.

30. The method of claim 1 wherein said member is developed by applying avaporous solvent for said softenable material to the imaging member,said vaporous solvent being at'least capable of softening saidsoftenable material to allow migration of said migration markingmaterial.

31. The method of claim 1 wherein said member is developed by heatingthe softenable material sufficiently to soften the softenable materialto allow migration of said migration marking material.

32. The method of claim 25 wherein the substrate is substantiallyelectrically insulating and the migration marking material comprisingelectrically photosensitive material is dispersed throughout the layerof softenable material and wherein before performing the charge andexposesteps of claim 25, the imaging member is precharged'by stepscomprising:

contacting the electrically insulating substrate to an electricallygrounded electrically conductive member. and

substantially uniformly electrostatically charging said member with acharge of opposite polarity from the said one polarity of charge used inthe subsequent charge step, while simultaneously substantially uniformlyflooding said member with activating electromagnetic radiation.

33. The method of claim 1 comprising separating the receiving sheet andthe imaging member.

34. The method of claim 29 comprising separating the receiving sheet andthe imaging member.

35. The method of claim 29 wherein said electrically insulating layerand said selective portions of said migration marking material aresubstantially removed and said selective other portions of saidmigration marking material are deposited on said substrate in image con-

1. AN IMAGING METHOD COMPRISING: PROVIDING AN IMAGING MEMBER COMPRISINGA SUBSTRATE SUPPORTING A LAYER OF SUBSTANTIALLY ELECTRICALLY INSULATINGSOFTENABLE MATERIAL CONTAINING MIGRATION MARKING MATERIAL, SAIDSOFTENABLE MATERIAL CAPABLE OF HAVING ITS RESISTANCE TO MIGRATION OFMIGRATION MARKING MATERIAL DECREASED SUFFICIENTLY TO ALLOW MIGRATION OFMIGRATION MARKING MATERIAL IN DEPTH IN SAID SOFTENABLE LAYER, FORMING ANELECTRICAL LATEN IMAGE ON SAID MEMBER, AND THEREAFTER PLACING ANELECTRICALLY CONDUCTIVE RECEIVING LAYER IN CONTACT WITH THE SOFTENABLELAYER OF THE IMAGING MEMBER, SAID ELECTRICALLY CONDUCTIVE RECEIVINGLAYER BEING ELECTRICALLY BIASES OR ELECTRICALLY GROUNDED, AND DEVELOPINGSAID MEMBER BY DECREASING THE RESISTANCE OF THE SOFTENABLE MATERIAL TOMIGRATION OF MIGRATION MARKING MATERIAL IN DEPTH IN THE SOFTENABLEMATERIAL AT LEAST SUFFICIENT TO ALLOW MIGRATION OF MIGRATION MARKINGMATERIAL AT LEAST IN DEPTH IN SAID SOFTENABLE MATERIAL WHEREBY THEMIGRATION MARKING SELECTIVELY MIGRATES IN A FIRST IMGAGE CONFIGURATIONTOWARD SAID CONDUCTIVE RECEIVING SHEET AND IN A SECOND IMAGECONFIGURATION COMPLEMENTARY TO SAID FIRST IMAGE CONFIGURATION TOWARDSAID SUBSTRATE.
 2. The method of claim 1 wherein the conductivereceiving layer is permeable to a fluid solvent.
 3. An imaging methodcomprising: providing an imaging member comprising a substratesupporting a layer of solvent soluble electrically insulating materialcontaining migration marking material, forming an electrical latentimage on said imaging member, providing an electrode closely spacedadjacent the free surface of said layer of solvent soluble electricallyinsulating material, said electrode being electrically grounded orelectrically biased without an insulating blocking layer between saidimaging member and said electrode, and providing a liquid solvent forsaid solvent soluble material between said layer of said solvent solublematerial and said electrode whereby migration marking materialselectively migrates in a first imagewise configuration toward saidsubstrate and in a second imagewise configuration complementary to saidfirst imagewise configuration toward said electrode.
 4. The method ofclaim 3 wherein said substrate is substantially electrically insulating.5. The method of claim 4 wherein the migration marking material isparticulate material and said particulate migration marking material isdispersed throughout the layer of solvent soluble material.
 6. Themethod of claim 4 wherein the migration marking material is in the formof a fracturable layer of migration marking material contiguous thesurfAce of the layer of the solvent soluble material spaced apart fromthe substrate.
 7. The method of claim 6 wherein the imaging memberadditionally comprises a second layer of solvent soluble electricallyinsulating material overlying the fracturable layer of migration markingmaterial.
 8. The method of claim 3 wherein the solvent is providedbetween the layer of solvent soluble material and the electrode byplacing said imaging member and said electrode in a volume of saidsolvent.
 9. The method of claim 4 wherein the migration marking materialcomprises electrically photosensitive material.
 10. The method of claim5 wherein the migration marking material comprises electricallyphotosensitive material.
 11. The method of claim 9 wherein theelectrical latent image is provided by steps comprising substantiallyuniformly electrostatically charging the surface of the imaging member,and imagewise exposing said member with an image pattern of activatingelectromagnetic radiation.
 12. The method of claim 10 wherein theelectrical latent image is provided by steps comprising substantiallyuniformly electrostatically charging the surface of the imaging memberwith a charge of a first polarity, and imagewise exposing said memberwith an image pattern of activating electromagnetic radiation.
 13. Themethod of claim 12 wherein before performing the charge and expose stepsof claim 12 the imaging member is pre-charged by steps comprising:contacting the electrically insulating substrate to an electricallygrounded electrically conductive member, and substantially uniformlyelectrostatically charging said member with a charge of oppositepolarity from said first polarity, while simultaneously substantiallyuniformly flooding said member with activating electromagneticradiation.
 14. The method of claim 12 wherein the migration markingmaterial in the imagewise unexposed areas of the imaging member migratein said first imagewise configuration toward the electrically insulatingsubstrate, and the migration marking material in the imagewise exposedareas of the imaging member migrate in said second imagewiseconfiguration complementary to said first imagewise configuration towardsaid electrode.
 15. The method of claim 3 wherein said layer of solventsoluble material is of a thickness in the range between about 1/2 andabout 16 microns.
 16. The method of claim 3 wherein said migrationmarking material is particulate material of average particle size in therange between about 0.01 and about 3 microns.
 17. The method of claim 16wherein said particulate migration marking material is of averageparticle size in the range between about 0.5 and about 1 micron.
 18. Themethod of claim 1 wherein said substrate is substantially electricallyinsulating.
 19. The method of claim 1 wherein said substrate issubstantially electrically conductive.
 20. The method of claim 1 whereinsaid substrate is substantially transparent.
 21. The method of claim 1wherein the migration marking material is particulate material and saidparticulate migration marking material is dispersed throughout the layerof softenable material.
 22. The method of claim 1 wherein the migrationmarking material is in the form of a fracturable layer of migrationmarking material contiguous the surface of the layer of softenablematerial spaced apart from the substrate.
 23. The method of claim 22wherein the imaging member additionally comprises a second layer ofsubstantially electrically insulating softenable material overlying thefracturable layer of migration marking material.
 24. The method of claim1 wherein the migration marking material comprises electricallyphotosensitive material.
 25. The method of claim 24 wherein theelectrical latent image is provided by steps comprising substantiallyuniformly electrostatically charging the surface of the imaging memberwith a charge of one polarity and imagewise exposing said member witH animage pattern of activating electromagnetic radiation.
 26. The method ofclaim 24 wherein said layer of substantially electrically insulatingsoftenable material is of a thickness in the range between about 1/2 andabout 16 microns.
 27. The method of claim 1 wherein said migrationmarking material is particulate material of average particle size in therange between about 0.01 and about 3 microns.
 28. The method of claim 27wherein said particulate material is of aveage particle size in therange between about 0.05 and about 1 micron.
 29. The method of claim 1wherein said member is developed by applying a liquid solvent for saidsoftenable material to the imaging member whereby portions of saidelectrically insulating layer and selective portions of said migrationmarking material are removed and selective other portions of saidmigration marking material migrate at least in depth toward saidsubstrate.
 30. The method of claim 1 wherein said member is developed byapplying a vaporous solvent for said softenable material to the imagingmember, said vaporous solvent being at least capable of softening saidsoftenable material to allow migration of said migration markingmaterial.
 31. The method of claim 1 wherein said member is developed byheating the softenable material sufficiently to soften the softenablematerial to allow migration of said migration marking material.
 32. Themethod of claim 25 wherein the substrate is substantially electricallyinsulating and the migration marking material comprising electricallyphotosensitive material is dispersed throughout the layer of softenablematerial and wherein before performing the charge and expose steps ofclaim 25, the imaging member is pre-charged by steps comprising:contacting the electrically insulating substrate to an electricallygrounded electrically conductive member, and substantially uniformlyelectrostatically charging said member with a charge of oppositepolarity from the said one polarity of charge used in the subsequentcharge step, while simultaneously substantially uniformly flooding saidmember with activating electromagnetic radiation.
 33. The method ofclaim 1 comprising separating the receiving sheet and the imagingmember.
 34. The method of claim 29 comprising separating the receivingsheet and the imaging member.
 35. The method of claim 29 wherein saidelectrically insulating layer and said selective portions of saidmigration marking material are substantially removed and said selectiveother portions of said migration marking material are deposited on saidsubstrate in image configuration.